To provide a two members surface contact coupling device by which a second member can be detachably fitted simply to a first member and which has a high fitting strength, no all-directional play generated to a coupled surface, a consistently steady coupling performance irrespective of repeated attachments and detachments, and a simple and inexpensive structure.

A locking member 61 is protruded on a fitting surface 41A of the first member 3. A locking hole 62 is formed on a coupling surface 6B of the second member 6 at least whose coupling surface side is formed from a metallic plate. The locking member is provided with a stepped portion from a base 61C fitted to the fitting surface to be formed integrally with a hooking portion 61A. A groove 61B opening continuously to its apical portion is formed in a central portion of a width direction at a side of the fitting surface of the hooking portion. At a position where the hooking portion is locked by a hole edge of the locking hole, a projecting portion 62A protruded inward by pushing stepwise the metallic plate constituting the coupling surface is formed to be inserted into an inside of the groove of the hooking portion in the locking member.